The present invention relates to an exposure technique, for example, relates to technology useful for a transfer technique etc. of circuit pattern in manufacturing processes of semiconductor integrated circuit etc.
When design rules for circuit elements and wirings become the order of submicron as high integration of semiconductor integrated circuits advances, in a photolithography process where circuit patterns on masks are transferred onto semiconductor wafers by using lights of g-line and i-line etc., the reduction of accuracy of circuit pattern transferred onto wafers becomes a serious problem. As a measure for improving such a problem, a phase shift technique preventing reduction of contrast of projected image by varying phases of light transmitting the mask is proposed. For example, Japanese patent application laid-open No. 173744/1983 discloses a phase shift where a transparent film is provided on one side of a pair of transmission domains between which a shielding domain is inserted, and phase difference is produced between lights transmitting the two transparent domains in the exposure, thereby the interference lights are weakened each other at the point on the wafer which would become a shielding domain originally (hereinafter referred to as "Levenson type" or "complementary type phase shift method").
Also, Japanese patent application laid-open No. 67514/1987 discloses a phase shift technique where after a part of the shielding domain of a mask is removed and a fine open pattern is formed, a transparent film is provided on either of the open pattern or the transmission domain existing in the vicinity thereof, and the phase difference is produced between the light transmitting the transmission domain and the light transmitting the open pattern, thereby the amplitude distribution of lights transmitting the transmission domain is prevented from spreading laterally (hereinafter referred to as "subshift type phase shift method").
Japanese patent application laid-open No. 140743/1990 discloses a phase shift technique where a phase shifter is provided on a part of the transmission domain of the mask and the phase difference is produced in the transmission lights, thereby the phase shifter boundary is emphasized (hereinafter referred to as "edge emphasized type phase shift method").